In a laser generator provided with a wavelength-conversion element, regarding the wavelength-conversion element, generally, the higher the beam intensity of the fundamental wave through the wavelength-conversion element, the more efficiently the wavelength conversion is performed. Accordingly, using a Q-switch, etc., a fundamental wave is converted to a pulsed one having high peak-output power, and thereby the beam intensity is instantaneously increased; thus, the wavelength conversion is efficiently performed. However, because the wavelength-conversion element has its breakage threshold for the beam intensity, if a laser beam whose intensity exceeds the breakage threshold is incident onto the element, a problem may occur that a crystal thereof is broken by the beam; therefore, in order to prevent the breakage of the expensive wavelength-conversion element, in a conventional laser apparatus, electric power to be supplied into a pumping light source, and pumping current and voltage have been limited (for example, refer to Patent Document 1).
Here, the breakage threshold is a value at which, if the beam intensity exceeds the value even by a little, the wavelength-conversion element is broken, which corresponds to the maximum absolute rating. Because the breakage threshold is determined by the structure of the crystal constituting the wavelength-conversion element and its coating, the value can be uniquely obtained in accordance with the wavelength-conversion element.
[Patent Document 1] Japanese Laid-Open Publication No. 2005-209965